PERSPECTIVE.

You are asked, O Painter, why the figures you draw on a small scale
according to the laws of perspective do not appear--notwithstanding
the demonstration of distance--as large as real ones--their height
being the same as in those painted on the wall.

And why [painted] objects seen at a small distance appear larger
than the real ones?

The right position of the artist, when painting, and of the
spectator (540-547)